Most 3G and 4G wireless systems support broadcast services (e.g., evolved multimedia broadcast multicast services (eMBMS) in Long Term Evolution (LTE) and broadcast, multicast services (BCMSCS) in the High Rate Packet Data (HRPD) system, also known as the Evolved Data Optimized (EVDO) system). These broadcast services along with digital video broadcast (DVB) and its variants DVB-Terrestrial (DVB-T), DVB-Satellite services to Handhelds (DVB-SH), etc. rely on orthogonal frequency division multiplexing (OFDM) air interface technology, wherein identical broadcast signals are transmitted from multiple base stations (BSs). For example, FIG. 1 is a wireless system according to the conventional art, wherein multiple base stations 1-201, 1-202, and 1-203 broadcast content (e.g., audio/video content) signals in a synchronized manner to user equipment UE 1-101 to achieve what is referred to as a single frequency network (SFN).
The performance of such a scheme depends on tight synchronization across the base stations participating in the SFN operation. In FIG. 1, physical layer synchronization entity (PLSE) 1-501 provides synchronization to base stations 1-201, 1-202, and 1-203, which are supporting multicast broadcast services (MBS). The desired synchronization may be at multiple levels: 1) at the physical level (provided by PLSE 1-501 and the associated links to the base stations 1-201, 1-202, and 1-203); 2) at the resource establishment level; and 3) at the applications level (e.g., using internet protocol multicast routing protocol (IMRP) over a backhaul network). However, even if PLSE 1-501 is able to achieve synchronization between baseband units (BBU) of each base station (a BBU is the device that controls radio functions of a base station), accurate synchronization between the transmit antennas of each base station is a major challenge because the timing differences between the BBU and antennas may be different for each base station. Thus, these so-called intra-base station timing differences (i.e., the different timing between the BBU and antenna of a base station) affect the overall synchronization of base stations in the conventional system of FIG. 1.
Additionally, as shown in FIG. 1, the content is delivered from content source 1-401 to base stations 1-201, 1-202, and 1-203 using IP multicast routing protocol via IMRP enabled routers (e.g., 1-301 and 1-302). However, IMRP protocols are usually not supported over the entire backhaul network. For example, FIG. 1 shows router 1-303 which does not have IMRP link functionality. Thus, undesired inefficiencies are introduced into the system of FIG. 1.
Furthermore, the above mentioned multicast broadcast services (MBS) are not currently defined for Network Multi-Input, Multi-Output (NMIMO) or cooperative multi point (CoMP) systems. However, this is likely to be the next area of activity in standardization and technology innovation.
As described above, the conventional art provides a system which relies on inter-base station synchronization and IMRP support over the backhaul network, which causes increased cost, implementation delays, provisioning complexity.